Olefin catalyst slurry feeding process and apparatus

ABSTRACT

IN MONO 1-OLEFIN AND DIOLEFIN PROCESSES AN IMPROVED METHOD AND APPARATUS FOR INTRODUCING A CATALYST SLURRY INTO THE POLYMERIZATION ZONE WHICH COMPRISES PRESSURIZING A CATALYST SLURRY THROUGH A TRANSPORT ZONE INTO SAID POLYMERIZATION ZONE, AND THEREAFTER PASSING SAID CATALYST SLURRY OVER A CONVEX SURFACE POSITIONED WITHIN SAID POLYMERIZATION ZONE SO AS TO DISPERSE SAID CATALYST SLURRY WITHIN SAID POLYMERIZATION ZONE IN THE FORM OF A SPRAY.

June 12, 1973 J. HEAVIN 3,738,975

OLEFIN CTALYST SLURRY FEEDING PROCESS AND APPARATUS Filed Jan. 18, 1971Rod amg/5f 27 5km/y hll.. Hh.. I l i ;I\ v @andar "United States PatentOice 3,738,976 Patented June 12, 1973 Filed Jan. 18, 1971, Ser. No.107,225 Int. Cl. C08f 1/56, 1/98 U.S. Cl. 26093.7 3 Claims ABSTRACT FII-IE DISCLOSURE In mono l-olen and diolefin processes an improvedmethod and apparatus for introducing a catalyst slurry into thepolymerization zone which comprises pressurizing a catalyst slurrythrough a transport zone into said polymerization zone, and thereafterpassing said catalyst slurry over a convex surface positioned withinsaid polymerization zone so as to disperse said catalyst slurry withinsaid polymerization zone in the form of a spray.

BACKGROUND OF INVENTION It is known that catalysts formed by combiningan organometallic compound of a metal of Groups II-A, II-B and III-A ofthe Periodic Table with a halide of a metal of IGroups IV-B, V-B or VI-Bof the Periodic Table are useful for polymerizing mono 1olefins anddiolens at low pressures and low temperatures to form resinouspolyolefins. These catalysts are conventionally produced by reacting theorganometallic compound with a metal halide in the presence of ahydrocarbon solvent to form a catalyst slurry.

Polymerization of oleiins such as ethylene and propylene isconventionally eifected with such catalysts by contacting the olefinwith the catalyst slurry in a bulk or mass polymerization zone in thepresence of an inert solvent such as benzene or -a saturated hydrocarbonlike isooctane, n-hexane, xylene, pentane or cyclohexane. Thepolymerization reaction is normally effected at a temperature of about 0to 200 C. and at pressures of about atmospheric or higher.

The introduction of the catalyst slurry to the polymerization reactor isgenerally complicated by severe fouling at the inlet port. This foulingis attributable to rapid polymerization of the monomer at the catalystinlet, resulting in plugging of the catalyst inlet port or, in the caseof a continuous polymerization loop reactor, plugging of thepolymerization reactor.

Accordingly, an object of the invention is to provide an improved methodand apparatus for the introduction of catalyst slurries into apolymerization reactor to prevent reactor fouling.

Another object of the invention is to provide an improved process forthe polymerization of oleiins to produce resnous polyolens.

Yet another object of the invention s to provide an improved olefinpolymerization process employing as an initiator a Ziegler-typecatalyst.

Other objects, advantages and features of the invention will be readilyapparent to those skilled in the art from the following description, thedrawings, and appended claims.

SUMMARY =OF INVENTION By the invention an improved method and apparatusfor the introduction of catalyst slurries into mono 1- oleiin anddiolefin polymerization zones is provided whereby the catalyst slurry ispressurized through a transport zone into the polymerization zone, andthereafter the catalyst slurry is caused to impinge upon a con- Vexsurface positioned within the polymerization zone in a manner so as todisperse the catalyst slurry Within the polymerization zone in the formof a spray.

DESCRIPTION OF DRAWINGS FIG. 1 is a schematic representation of theinvention as applied to an olen polymerization process utilizing aconventional loop reactor.

FIG. 2 is a detailed cross-sectional, elevated view of the novelcatalyst feeding apparatus.

IDESCRIPTION IOF INVENTION The invention is applicable to mono 1olen anddiolefin polymerization processes wherein the olefin polymerizationreaction is conducted in a polymerization zone containing less than 50weight percent of an inert organic solvent. The invention isparticularly applicable to bulk or mass polymerization processes whereinthe olefin monomer feed to the polymerization reaction zone include mono1-olelins such as ethylene, propylene, butenel, pentene-l, hexene-l,4-methyl-l-pentene, 3methyl butene-l, and styrene, and/or conjugateddienes of 4 to 8 carbon atoms per molecule such as 1,3-butadiene,isoprene, 2,3-dimethylbutadiene, 2-methoXy-1,3hexadiene, 1,3-octadiene,and the like.

In the polymerization of oleiins such as described above, it is knownthat catalysts formed by combining an organometallic compound of a metalof Groups II-A, II-B and III-A of the Periodic Table with a solid halideof a metal of Groups IV-B, V-B or VI-B of the Periodic Table are usefulfor polymerizing such olens at low pressures and low temperatures toform resinous polyolens. In preparing such catalysts, particularlysuitable organic metallic compounds are the alkyl, especially the loweralkyl compounds, of the metals of Groups II-A, II-B and III-A, such asaluminum, Zinc, cadmium and beryllium. Organometallic compounds in whichthe metal is attached to cycloalkyl radicals of 3 to 7 carbon atoms oraromatic radicals such as phenyl, as well as halogenated compounds suchas dialkyl aluminum chlorides, are also suitable.

Some of the solid metal halides useful in preparing the aforementionedcatalysts are the halides, particularly the chlorides and bromides, oftitanium, zirconium, vanadium, chromium, molybdenum and tungsten, withtitanium and vanadium trichlorides and tetrachlorides being preferred,as well as the oxyhalides of such metals including vanadium oxychloride,and complexes such as AlCl3 2TiCl3.

As specific examples of suitable organometallic compounds useful informing the aforementioned catalysts may be mentioned the dialkylcadmiums, such as diethylcadmium, dimethylcadmium and diisobutylcadmium,the dialkylzincs, such as diethylzinc and dibutylzinc, thetrialkylaluminums and dialkylaluminum hydrides such asdiisobutylaluminum hydride, diethylaluminum hydride, trimethylaluminum,triethylaluminum, tripropylaluminum, triisobutylalumiuum anddiethylaluminum chloride, the cycloalkyl metal compounds such astricyclohexylaluminum, and the aryl metal compounds such asdiphenylcadmium and dinaphthylzinc. The alkyl group on such compounds isadvisably a lower alkyl and particularly such a group having 1 to 4carbon atoms.

'Ihese catalysts are conveniently produced by reacting theorganometallic compound with the metal halide in the presence of ahydrocarbon solvent such as isooctane, n-heptane, Xylene or benzene. Themolar ratio between the organornetallic compound and the halogenatedmetal may be varied within wide limits. A ratio of about 0.25 to about 4mols of halogenated compound, such as a titanium or vanadiumtrichloride, to 1 mol of the organometallic compound is suitable. Atypical catalyst system could comprise a catalyst slurry composed ofn-heptane,

triisobutylaluminum and solid titanium trichloride with thetriisobutylaluminum and titanium trichloride in an equimolar ratio. Suchcatalyst slurries are applicable in the practice of the invention ashereinafter described.

In addition to the above-described catalyst slurries, the invention isapplicable to catalyst slurries comprising an inert organic solvent andthe combination of (a) an organometallic compound in which the metaltherein is selected from a member of the group consisting of GroupsII-A, II-B and III-A of the Periodic Table, (b) a metal halide in whichthe metal therein is selected from a member of the group consisting ofGroups IV-B, V-B and 'VI-B of the Periodic Table, and (c) an additivecompound selected from the group consisting of those polyamines,polyethers, aminoethers, aminoalcohols and hydroxyethers which normallychelate metals.

The organometallic compounds and the metal halides used in thesecatalyst compositions are those which are described hereabove and theratios of these components are the same as employed in theabove-described catalysts. For a complete description of additivecompounds which may be included in preparation of the catalyst slurriesof this invention reference is made to U.S. 3,219,648.

A suitable method of preparing the catalyst slurries utilizing theadditive compound comprises combining at least one of the additivecompounds with the organometallic compound and the metal halidecomponent in an inert hydrocarbon solvent, such as isooctane, n-heptane,xylene or benzene. In a second suitable method of preparing the catalystslurry, the additive compound can be combined with either theorganometallic compound or the metal halide before the other is added tothe hydrocarbon solvent to form the catalyst slurry, as the order ofaddition does not critically affect the polymerization process.

Thus, by way of illustration, an aminoalcohol additive compound may beadded to titanium or vanadium trichloride prior to the addition oforganometallic compound to the solvent, or the additive may be added tothe organometallic compound prior to the addition of titanium orVanadium trichloride, Furthermore, two or more additives can be employedin the preparation of catalyst slurries.

In general, up to 0.5 mol of the additive compound per mol oforganometallic compound is suitable for producing the catalyst slurries.However, about 0.05 to about 0.5 mol of additive for each mol oforganometallic compound is preferably used. Amounts less than 0.05 canbe employed but with some sacrifice in polymerization efficiency.

Heating the catalyst composition when combined in an inert solvent atmoderately elevated temperature improves the reactivity of the catalyst.By heating is normally meant temperatures of about 60 to 65 C., althoughwith some additive compounds higher temperatures of up to 100 C. orhigher can be utilized.

Referring to FIG. 1 and FIG. 2, the invention will hereafter bedescribed as it relates to a propylene polymerization process conductedin a loop reactor. Propylene is continuously introduced at the rate of 9gallons per hour via conduit means 10 to a conventional 32 gallonreactor 11 comprising a continuous loop. A reaction mixture comprisingpropylene, polypropylene, catalyst and hydrocarbon diluent iscontinuously passed in a clockwise direction through loop 11 via atransporting means such as an impeller 12 driven by a motor means 13. Aheptane diluent is introduced via conduit means 14 and conduit means 10to reactor 11 at a rate sufficient to maintain a circulating mixturecontaining about 10 weight percent polymer solids. The concentration ofdiluent maintained in the circulating reaction mixture is less than 50percent by weight of the reaction mixture and in this example willcomprise about 10 percent of the reaction or circulating mixture. Aneffluent mixture comprising polypropylene, heptane and propylene iswithdrawn from loop reactor 11 via conduit means 16 and valve means 17.

A reaction temperature in the range of -180 F. is maintained in thecirculating mixture. A reaction pressure of about 560 p.s.i. ismaintained within reactor 11. A catalyst composition comprising 5.9weight percent tetramethylmethylenediamine, 29.4 weight percent titaniumtrichloride, and 64.7 weight percent triethylaluminum is combined with aheptane solvent and the resulting catalyst slurry is introduced via theconventional pumping means 19, conduit 20 and inlet channel means 21into reactor 11. The concentration of the catalyst components in theheptane solvent is 0.2 weight percent.

The etiluent reaction mixture is withdrawn from reactor 11 via conduitmeans 16 at a rate equivalent to the feed rate of propylene, heptane andcatalyst components to the reaction zone. The rate of production ofpolypropylene in the polymerization reactor is 5 pounds per hour at aproductivity rate of 1300 pounds of polymer produced per 1 pound ofcatalyst components introduced into reactor 11.

Although not shown in FIG. 1, temperature control of the circulatingreaction mixture can be effected by employing indirect heat exchangezones such as illustrated in U.S. Pat. 3,451,785. As described in thesaid patent, each straight pipe section of the loop can be encased witha jacket containing an inlet and an outlet for the introduction andremoval, respectively, of a heat exchange `fluid.

The catalyst slurry is introduced into reactor 11 via a dip tube 21having a channel opening in communication with the interior of reactor11. Dip tube 21 can be positioned so as to permit introduction of thecatalyst slurry into the center of loop reactor 11 or, alternatively,dip tube 21 can be positioned adjacent to the interior wall of reactor11. As illustrated, dip tube 21 has a concaveshaped open end, theconcave shape being complementary to the convex surface of a hereafterdescribed closure member 26.

A rod 23 is positioned within dip tube 21 and is capable of being movedforward or downward into reactor 11 responsive to a hereafter describedpressure to attain the position illustrated in FIG. 2. As illustrated,rod 23 is spring-loaded so as to maintain the rod 23 normally in arearward or upward position, with the surface of closure member 26immediately adjacent to the open end of dip tube 21, thereby preventingthe ow of solids or fluid through dip tube 21 to reactor 11 when rod 23is in its rearward position.

As illustrated in FIG. 2, closure member 26 is spheroid shaped and isaffixed to rod 23. The upper surface of closure member 26 is shaped soas to effect a tight seal with the opening of dip tube 21 when rod 23 isin its rearward position. Although closure member 26 has beenillustrated as spheroid in shape, it is Within the scope of theinvention to employ closure members having a variety of shapes with therequirement that each closure member shall have a connex upper surfacein the manner illustrated in the drawing.

Although opening 24 as shown is concave shaped, is is also within thescope of the invention to employ open-ended dip tubes wherein the openend surface parallels the center line of the reaction vessel.

Dip tube 21 is positioned within reactor 11 by means of a conventionalflange 31, which is bolted to the inlet ange of reactor 11. As furthershown in FIG. 2, means for guiding the movement of rod 23 and foreffecting a high pressure seal comprises a conventional stuffing box 27.Packing 28 is positioned within stung box 27 and adjacent to rod 23. Apacking gland 29 and packing gland nut 30 complete the stuing boxassembly.

As described above, the catalyst slurry is transported via pumping means19, conduit 20 and dip tube 21 into reactor 11. Pumping means 19 impartsa pressure to the catalyst slurry in excess of the pressure in reactor11 and sucient to force rod 23 and containing closure member 26 forwardto the open position. The catalyst slurry is transported from dip tube21 over the upper conlVex-shaped surface of closure member 26 and awayfrom the point of communication between dip tube 21 and reactor 11 andthroughout the interior of reactor 11 in the form of a spray, therebypreventing catalyst retention and polymer accumulation at the catalystinlet.

With no catalyst slurry being transported through conduit 20 and diptube 21, spring 22 operates so as to maintain the upper convex surfaceof closure member 26 in closed relationship with the opening of dip tube21, thereby preventing any dow from reactor 11 through dip tube 21.

Although the invention has been described with reference to specificmaterials, embodiments and details, various modifications and changes,within the scope of the invention, will be apparent to those skilled inthe art and are contemplated to be embraced in the invention.

What is claimed is:

1. In an olen polymerization process which comprises polymerizing anolefin selected from the group consisting of mono 1olens and dioletns ina polymerization zone in the presence of a catalyst and at apolymerization temperature and pressure; the improvement which comprisespressurizing a catalyst slurry through a transport zone into saidpolymerization zone, and thereafter passing said catalyst slurry over aconvex outer surface of a closure member positioned within saidpolymerization zone and adjacent to the outlet of said transport zone soas to disperse said catalyst slurry within said polymerization zone inthe form of a spray.

2. The process of claim 1 wherein said catalyst slurry comprises aninert hydrocarbon solvent, an organometallic compound, a metal halideand an additive compound selected from the group consisting of thosepolyamines, polyethers, aminoethers, aminoalcohols and hydroxyetherswhich normally chelate metals.

3. The process of claim 1 wherein said olefin is selected from the groupconsisting of ethylene and propylene.

References Cited UNITED STATES PATENTS 3,257,362 6/ 1966 Norwood .i260-94.9 P

894,978 8/ 1908 Peache 239--88 1,225,703 5/1917 Davol 239-88 2,088,0077/ 1937 Zumbusch 239--5 2,119,966 6/1938 ScOtt 239--5 3,182,050 5/1965Irvin 260-94.9 B

JAMES A. SEIDLECK, Primary Examiner A. HOLLER, Assistant Examiner U.S.Cl. X.R.

23-288 E; 239-87; 260-942 R, 94.3, 94.9' P

